X-ray sensitive screen



May 9, 1950 J. H. SCHULMAN ET AL 2,506,749

X-RAY SENSITIVE SCREEN Filed May 27, 1948 JNVENTORS JAMES H. SCHULMANLYLE W. EVANS BY ROBERT GINT ATTORNEY Patented May 9, 1950 UNITED STATESeerie E51 X-RAY SENSIHVE SCREEN" J'amevH. Scli'uhnan; Washington, D;(1;, LyleLWJ.

E'vans; Emporium; Pa., and Robert Ginth'err" Washington, DIG.

Application-May 27, 1948; Seria'LNm: 29;60-7

7"Claims; (31'. 250 -71) (Granted... under. the act oti March: 3,.1883;:,ast.-

amemledApril 30,. 1928; 370%} 757-) This invention relates to the use ofnon- Theepresentiinventioni.involves, vonthe. other photographicchemical materials inthe-detecting hand not aprocess for. altering therate of the and.recordingzof highafrequency radiation, .suchemissionoiabsorbederadiant energy, but rather; Y- and sam-maray radiation,and-their. for permanentlyaltering thephysicallnature of.

applications:torradiography. and diffractiom thehaffectedmaterialsltorwhichwe.shallapply, Certain materials, genericallyreferred. to. as broadly, the term phosphors) by means ofone: phosphors,have been widely used ,forithis pmtype.,.of.radiation in isucha way.that their charposerin X-ray'workr.inconjnnctionrwithphotoacteristicsundercertain, other radiations are graphic plates-or film. clearlyaltered'e.

Inithislatt riana y th ymit a tinicradh 19 Itiisithe. general. object.of this-invention to. ation asa; directv resultrof. simply being.-irradi=- rovideavmethodifor. detectingiby means of one" ed with f y ande y augment the. type of radiation the-permanent changes brought.photochemical.-. reduction brought about as b t. inmcertainm phosphonmaterials by means" primariiy a functionofthe. Xerays. Thusetheyf,nother.typeioilradiation, act as intensifiersf? in; that they reducethe: Another object is to provide a method of: amoun f X-r r n r y;- rir f r a q permanently. aifecting. certain materials. by X film blaceninaand ns q n y th r qu s ray or. gamrnaray radiation so that theeffect. exposure time lfiubeeu'rr-ent i It il d can atiany later...time. be..detected by subsequent u that the phenomenon h r involvedis-p..r0n-= ultra=vio1et radiation-treatment. r y fi s rather" 111131!20 It is the particular. object of the invention to phosphorescence eventhough the. radiation. provide. a. new and, improved, radiographic oremitted isnot=necessarily visible. Thiszis becauses diffractiontechnique wherein certain the luminescence.." (broadyusage)continuessoniy phgtographic ,phosphon material is permanentlyduring-theperiod of exposureyto:X-rayswhereas: affected; by X-ray; or.gamma. ray, radiation; phosphorescence is: a; phenomenon: operative;differentially, according tcrthejntensity of the:afterthepl'imalyxradiationhas ceased; transmittedmr.diffiractedabeam soflas-to form a An th r pl of: a ph sph is; the shadow-graph(radiographic image); or. dif-' fluoroscopic screen? which-is 'madenof'at-closely? fraction;pattern on the aflected phosphgr relatedluminescent: material differing": only in? terial, andzsubsequentlyirradiatingsaid material; that its emits radiation falling withinthe=visible 39 with. umwviolet 7 radiation t bring t aid.

range of :thespeetrum; and thusdoesaway with shadowgmphw or ttenegativdyp through need a? Photographic" Operation when visiblefiuorescence...oi; then-unaffected portion. of observation is desired:the,

Some phosphor. materiaisafter; treatment :with; The presentimventionhconsists gin t progess exhibit to val'ying'idegrees' trueottreating,certain.pl'iospl ior materials with hishphorescence orafterrglowin-ieither the visible :on; frequency, radiationhavingmazwavefl length invisible: ranger. Recentlyphosphorsrhaveebeenitween (L001 A and 500 A such as X mys ongam?developedinirwhich.the:aiterg1ow. (Whiehr-hapr manmysf andtherebyfdecreasmgntheirvlumines cence under:subsequentradiationtreatment-,with.

i iv i 'dvmateriais -be peratures. The. radiation. rate. of. these.phoszfbgwen'ultm 9 radian)?! Sal W phors is increased lby-raising thetemperature mg stmligly lumutescent F t vlslbledange and also bysubjecting we; material to inf??? under said;- u1 tra-.-v 1o1et;.radiation: priorto exred-radiation posure to. said. high-frequency.radiation, in Thus it is seen that the prior art of" phosphor"o-ther'words,theiprocessof destmy-mgi some materials is limitedtd cases:where" the lumi' nescence is" a' direct I6SU'1U'OfTth6 primarvirradation, whether said"luininescencebeconcurrent ri inally visiblyfluorescent under. the parwith' (fluorescent) or'subsequent'to'(phosphores tiwlal'f ultmwlolet Tadlatloni cent) said irradiation. Inother" words the 0 Our: J -pending: app a fln; la phenomenon of"luminescencefo11ovvs= immedi 2 9L606; filed of evenxdatevherewith;wehave disatel-y and necessarily"asaresult of "the or-iginair' closedxatype of; phosphor material and-=awtech--- the? ultra-violetluminescentresponsivity by" means: of X-rays: In all. cases the-"material isexcitation, andj. further treatment of any: kind-1* nique-zembodyingits' usage, in: which: ultra-violet is oneaffctingoniy-the rateofluminescent de responsivity is created by treatment with X cay f rays:W1'aetheror:*-not a; material: is-original y luminescent ornon-luminescent under ultraviolet radiation may depend on the wavelengthof said radiation. Thus, it is necessary to know the effect of aparticular ultra-violet radiation on a particular phosphor prior to itsexposure to X-irradiation, and to bring out the efiect of saidirradiation with the same ultra-violet radiation after exposure.Although there is probably for every phosphor an optimum ultra-violetwavelength at which the intensity of contrast is a maximum, anyradiation under which an appropriate phosphor is originally luminescent(as in this application) or non-luminescent (as in our co-pendingapplication) is operative.

In this invention a phosphor material which is normally luminescent (inthe visible range) under a given ultra-violet radiation is reduced inthe intensity of its luminescence upon being irradiated byhigh-frequency radiation having a wave length between 0.001 A. and 500 Asaid reduction being proportional to the quantity of radiant energyreaching the phosphor material. Thus the invention constitutes a meansof making negative radiographic images (shadowgraphs) or diffractionpatterns of an opaque object.

An advantage of the invention is that a permanent record of the image orpattern is made without the employment of photographic means. The imageor pattern, resulting from a permanent change in the nature of thephosphor material, is not susceptible to dissipation with time,temperature (except possibly at high levels), or to continuedapplication of the ultra-violet radiation.

The phosphor material used in a preferred embodiment of this inventionis a solid solution of salts of lead. and manganese and at least oneother salt wherein the Pb++-Mn++ combination constitutes the activatoringredient. However, phosphors containing other activators, for example,Sn++, may be used. This phosphor material may be prepared by fusiontogether of the respective components and subsequent solidification, orby precipitation from a concentrated aqueous solution of saidcomponents. In the preparation of the lead-containing phosphors theprecipitation method is preferred since volatilize.- tion may occurduring fusion. The relative quantities are not critical, only a smallamount of the active ion or ion combination being required to make aphosphor luminescent under ultraviolet radiation. The solid solution isground mechanically (if prepared by fusion) to a particle size in theorder of 200-300 mesh and applied to a suitable backing material to forma phosphor screen.

As an illustration of one way in which the process may be carried outthe accompanying drawings are shown and the following proceduredescribed:

A phosphor material is prepared by fusion or precipitation of a mixtureof one part lead chloride, one part manganese chloride and fifty partssodium chloride. The material is then ground and mounted on a suitablebacking material. If it is now examined under ultra-violet radiation,for example 2537 A it will be seen that the material luminesces brightlyemitting visible light. This particular radiation is desirable since itis conveniently produced (by germicidal lamps) and creates a strongluminescence in this phosphor.

The screen is then placed in the film position I in a radiographicassembly, Fig. 1, arranged for example, to X-ray a steel flange 2, and ahigh frequency radiation 3 such as from a tungsten target 1 operating at30 kv. (0.5-1.0 A.) is directed toward and through the flange. Afterexposure the phosphor screen is again examined, Fig. 2, underultra-violet radiation IU of wave length 2537 A. and it is observed thatthe screen H has lost much of its luminescence and now is quite darkover the directly exposed areas. Furthermore, the loss of luminescenceis proportional to the intensity of the X-irradiation reaching thescreen. Of course, the practical value of such a technique lies inshowing up differences in density in the X-rayed object, such as resultfrom internal defects, rather than differences in thickmess.

The above example is intended to be illustrative and not limitative ofthe invention except as to the extent defined in the herewith appendedclaims.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposesWithout the payment of any royalties thereon or therefor.

What is claimed is:

1. The method of permanently reducing luminescent responsivity to agiven ultra-violet radiation in a phosphor material originallyresponsive to said ultra-violet radiation, said material consistingessentially of a solid solution of one part each of a lead salt and amanganese salt and fifty parts of sodium chloride, comprising subjectingsaid ultra-violet responsive material to high-frequency radiation havinga wave length Within the range of 0.001 A. to 500 A.

2. In apparatus for the preparation of a permanent, negative withrespect to luminescence, radiographic image or a diffraction pattern ofan opaque object on a luminescent screen, the combination of a phosphorscreen having an X-ray sensitive, fluorescent responsivity to a givenultraviolet radiation consisting essentially of one part each of a leadsalt and a manganese salt and fifty parts of sodium chloride,ultra-violet radiation means providing said radiation, andhigh-frequency radiation means providing radiation having a wave lengthwithin the range of 0.001 A. to 500 A.

3. In apparatus for the preparation of a permanent, negative withrespect to luminescence, radiographic image or a diffraction pattern ofan opaque object on a luminescent screen, the combination of a solidsolution of one part each of a lead salt and a manganese salt and fiftyparts of sodium chloride mounted on a suitable backing material,ultra-violet radiation means providing a radiation having a wave lengthbetween 2400 A. and 3000 5., and high-frequency radiation meansproviding radiation having a wave length within the range of 0.001 A. to500A.

4. In the preparation of a permanent, negative with respect toluminescence, non-photographic, radiographic image of an opaque metalobject upon a luminescent screen, the method comprising, placing in thefilm position in a radiographic assembly a phosphor screen luminescentunder a given ultra-violet radiation comprised essentially of a leadsalt and a manganese salt of about one part each and sodium chloride ofabout fifty parts, transmitting high-frequency radiation of a wavelength within the range of 0.001 A. to 500 A. to-

ward and through said metal object, thereby permanently affecting saidphosphor screen, and subsequently irradiating said permanently affectedphosphor screen with said ultra-violet ra" diation to bring out,negatively, the image of said opaque object.

5. The method of detecting the permanent reduction in the luminescentresponsivity of a phosphor material responsive to a given ultra-violetradiation brought about by exposure of said material to X-ray radiation,said material consisting essentially of one part each of a lead salt anda manganese salt and fifty parts of sodium chloride comprisingsubjecting said X-ray exposed material to said given ultra-violetradiation.

6. The method of evaluating the intensity of a high-frequency radiationof wave-length between 0.001 A. and 590 A. comprising, irradiating aquantity of phosphor material consisting essentially of one part each ofa. solid solution of a lead salt and a manganese salt and fifty parts ofsodium chloride with an ultra-violet radiation having a wave-length from2400 A. to 3000 A. to produce a given fluorescent response, irradiatinga quantity of said phosphor material with said high-frequency radiation,and irradiating said irradiated quantity of phosphor material with saidultra-violet radiation to produce a different fluorescent response, thedifference in the respective fluorescent responses being an evaluationof the intensity of the high-frequency radiation.

7. The method of preparing an image of a pattern of high-frequencyradiation having a wavelength between 0.001 A. and 500 A, comprising,forming a permanent, invisible image of said pattern on an ultra-violetresponsive, X-ray sensitive phosphor screen comprising essentially onepart each of a solid solution of a lead salt and a manganese salt andfifty parts of sodium chloride mounted on a suitable backing material,by exposing said screen to said pattern, and forming a fluorescent,visible, negative image of said pattern by exposing said exposedphosphor screen to ultra-violet radiation having a Wave-length between2400A. and 3000 A.

JAMES H. SCHULMAN.

LYLE W. EVANS.

ROBERT GINTHER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,418,240 Curie et al May 30,1922 2,213,138 Hayward Aug. 27, 1940 2,247,112 Batchelor June 24, 19412,360,326 Adrian et al Oct. 17, 1944 OTHER REFERENCES Luminescent andTenebrescense as applied to Radar, by H. W. Leverenz, R. C. A. Review,vol. 8, N0. 2, June 1946, Fig. 15.

1. THE METHOD OF PERMANENTLY REDUCING LUMINESCENT RESPONSIVITY TO AGIVEN ULTRA-VIOLET RADIATION IN A PHOSPHOR MATERIAL ORIGINALLYRESPONSIVE TO SAID ULTRA-VIOLET RADIATION, SAID MATERIAL CONSISTINGESSENTIALLY OF A SOLID SOLUTION OF ONE PART EACH OF A LEAD SALT AND AMANGANESE SALT AND FIFTY PARTS OF SODIUM CHLORIDE, COMPRISING SUBJECTINGSAID ULTRA-VIOLET RESPONSIVE MATERIAL TO